Optimum Deposition Conditions Research Articles

Functional interlayers with controlled adhesion developed for polymer composites

The plasma coating of glass fibers is an alternative technology to the wet chemical processes employed for the commercial sizing used for glass-fiber-reinforced polymer composites. A polymer-like film prepared by plasma polymerization can be used as a compatible interlayer between the glass fiber and the polymer matrix. The shear stress distribution across the interphase in a fiber-reinforced polymer composite indicates that the interfacial adhesion at the interlayer/fiber interface is the key factor influencing the performance of the polymer composite. The plasma-polymerized tetravinylsilane deposited at an enhanced effective power was tested as an adhesion film on planar glass substrate using a nanoscratch test. The work of adhesion was used as a measure of film adhesion based on the analysis of the scratch mechanics. An enhanced effective power (0.1–10 W) resulted in a film adhesion change only in the region of 30% for plasma-polymerized tetravinylsilane. The addition of oxygen gas to the tetravinylsilane monomer enabled the depositing of films over a wide range of film adhesions. A 3.7-fold increase in film adhesion was revealed for optimized deposition conditions. For a given film, a strong correlation was found between the shear strength of the polymer composite with glass fibers coated by plasma polymer film and the corresponding film adhesion on planar glass substrate determined using the nanoscratch test.

Electrodeposition of Ag Catalysts for Electrochemical CO2 Reduction

The electrochemical reduction of CO2 to useful products has been considered as a promising technology for reducing the greenhouse gas [1]. Among the various products, CO has been targeted in this study since it can be directly used in Fischer-Tropsch process [2]. For CO production, Ag has received the great attention due to its electrocatalytic performance and moderate price compared to other noble metals [3, 4]. To improve the performance of the catalysts, structure engineering to enlarge the surface area have been widely investigated [4, 5]. In particular, fabrication of nano catalysts with large surface area on the carbon paper is required for MEA-type CO2 electrolyzer for large scale production. For this purpose, electrodeposition is efficient method to fabricate the catalyst on the carbon paper for various gas reduction reactions. In addition, the morphologies and coverage of catalyst layer could be easily controlled using various deposition method such as pulse electrodeposition [6, 7]. In this research, a galvanostatic pulse electrodeposition method was used to fabricate the Ag catalyst on the carbon paper. Increasing the off-time value during the galvanostatic pulse deposition, large surface area was developed. Using the optimized deposition conditions, high current density of CO production was achieved with large surface area of Ag catalysts. The CO production was further enhanced by removal of produced gases bubbles with surfactant.

The Effect of Various Catalyst on In-situ Synthesis of Carbon Nanotubes on the Glass Mat Using Thermal Chemical Vapor Deposition Method

The main aim of this research work is in situ synthesis of carbon nano tube (CNT) on nonwoven glass mat. Different types of catalyst were used and the effect of them on growth of carbon nanotubes on glass mat was investigated. The process was considered as variable catalysts to achieve optimal conditions for CNT deposition on glass mat. In this research, iron, cobalt, copper and nickel were used as catalysts and acetylene gas was used as the hydrocarbon source. Also, argon was used as a carrier gas. In first step, samples were coated by mentioned catalyst using plasma sputtering method. The thickness of the catalyst on the surface of samples was fixed at 100 nm. In second part, thermal chemical vapor deposition (TCVD) system was used for growth of carbon nano tubes. Scanning electron microscopy (SEM) and raman spectroscopy, thermogravimetric analysis (TGA-DTG) and transmission electron microscopy (TEM) were used for investigating the morphology and quality of produced CNT. Electrical conductivity was observed and compared on both untreated and coated glass mat. The results show that, by pre sputtering of samples with nickel, the quality of CNT on the surface of glass mat will be improved and the resistivity of samples reach to 610 Ω.

Effect of crystallization strategies on CH3NH3PbI3 perovskite layer deposited by spin coating method: Dependence of photovoltaic performance on morphology evolution

In this paper, the effects of humidity, annealing temperature and deposition method including one step method, sequential deposition rout and hot casting technique are investigated on the morphology of perovskite layer. The optimal conditions for deposition of perovskite layers are introduced. Formation and growth of CH3NH3PbI3 perovskite crystals by these procedures leads to completely different crystal shapes and sizes and as a result different cell efficiency and environmental stability. Humidity and annealing temperature have great effect on the morphology of perovskite layer in one step method. It was found that in one step method by increasing the humidity from <10% to ~40% (during spin coating and annealing the CH3NH3PbI3 perovskite) morphology of the spin coated layer evolves from mostly ribbon shape with a large number of voids to layers comprising hollow fibers. However increase of the annealing temperature from 100 to 140 °C results in decreasing the diameter of the formed hollow fibers. In hot casting technique, by controlling the casting temperature, a very compact flat layer including lotus leaf-like morph with fewer pinholes can be created. Cells fabricated using CH3NH3PbI3 cuboid crystals grown by sequential deposition rout showed the highest photocurrent and power conversion efficiency (4.8%). However deposited layers via sequential deposition rout and then the cells fabricated using them are not chemically as stable as those prepared by one step method for long time performance due to humidity induced degradation of large crystal of CH3NH3PbI3 to smaller size.

Pulsed laser/ electrodeposited CuBi2O4/BiVO4 p-n heterojunction for solar water splitting

CuBi2O4 is regarded as p-type candidate for photoelectrochemical water splitting due to its attractive thermodynamic and band structure features. In this work, we present the optimization of CuBi2O4 thin films synthesized by electrodeposition method on FTO glass substrate. CuBi2O4/BiVO4 heterojunction were further fabricated by depositing BiVO4 on CuBi2O4 with pulsed laser deposition method. The influence of parameters such as the electrodeposition time and pulse count of PLD deposition on performance of the heterojunctions was studied. The films were characterized by X-ray diffraction, SEM, UV–Vis and electrochemical properties. The optimal deposition condition for CuBi2O4 sample was found to be electrodeposition for 20 min and annealing at 500 °C for 4 h. Pulse laser deposition (PLD) was used for the first time to deposit BiVO4 on CuBi2O4 to form p-n heterojunction. The photoelectrochemical behavior study of sample with different BiVO4 thin film thickness showed that the optimal photocurrent is − 0.25 mA/cm2 in 0.1 M Na2SO4 (pH = 6), which is doubled comparing to that of the bare CuBi2O4 film.

Low loss poly-silicon for high performance capacitive silicon modulators.

Optical properties of poly-silicon material are investigated to be integrated in new silicon photonics devices, such as capacitive modulators. Test structure fabrication is done on 300 mm wafer using LPCVD deposition: 300 nm thick amorphous silicon layers are deposited on thermal oxide, followed by solid phase crystallization anneal. Rib waveguides are fabricated and optical propagation losses measured at 1.31 µm. Physical analysis (TEM ASTAR, AFM and SIMS) are used to assess the origin of losses. Optimal deposition and annealing conditions have been defined, resulting in 400 nm-wide rib waveguides with only 9.2-10 dB/cm losses.

Enhanced solar cell performance by optimization of spray coated CZTS thin film using Taguchi and response surface method

The present study aims to investigate the optimum deposition conditions for preparation of CZTS thin films using the spray pyrolysis method. CZTS is a vital semiconducting material now days, as it requires the constituents, which are non-toxic and easily available as well. The Taguchi approach is implemented for optimization. Major quality control parameters considered are: copper to zinc plus tin (Cu/Zn + Sn) ratio; zinc to tin (Zn/Sn) ratio; substrate temperature; and spray time. Three levels of each parameter are selected. This attributes L9 (34) orthogonal array according to Taguchi design. The signal to noise (S/N) ratio and an analysis of variance is carried out to achieve an optimum combination of quality control parameters. In the present study, thin films are optimized in terms of the band gap. The solar cell is fabricated for each experiment and for an optimum combination as well. A novel cell fabrication (inverted) is introduced which can cover full light spectra. The cell is fabricated as FTO/i-ZnO/Al:ZnO/CdS/CZTS/CuS/FTO. More than 17% improvement in efficiency is observed by the cell fabricated using optimum condition than the best efficiency achieved by orthogonal array 2, among all 9 arrays. Furthermore, to achieve specific optimum condition, response surface methodology (RSM) is implemented. The RSM is carried out for a multiple response (band gap and efficiency). The films are characterized by X-ray diffraction and field emission scanning electron microscopy. Optical properties are studied by UV–Visible spectroscopy. The elemental study is carried out using energy-dispersive X-ray spectroscopy.

Deposition of hydrogenated silicon clusters for efficient epitaxial growth

Epitaxial silicon thin films grown from the deposition of plasma-born hydrogenated silicon nanoparticles using plasma-enhanced chemical vapor deposition have widely been investigated due to their potential applications in photovoltaic and nanoelectronic device technologies. However, the optimal experimental conditions and the underlying growth mechanisms leading to the high-speed epitaxial growth of thin silicon films from hydrogenated silicon nanoparticles remain far from being understood. In the present work, extensive molecular dynamics simulations were performed to study the epitaxial growth of silicon thin films resulting from the deposition of plasma-born hydrogenated silicon clusters at low substrate temperatures under realistic reactor conditions. There is strong evidence that a temporary phase transition of the substrate area around the cluster impact site to the liquid state is necessary for the epitaxial growth to take place. We predict further that a non-normal incidence angle for the cluster impact significantly facilitates the epitaxial growth of thin crystalline silicon films.

DC magnetron sputtered aligned ITO nano-rods with the influence of varying oxygen pressure

Aligned Nano rods of transparent conducting indium tin oxide (ITO) were deposited on glass substrates using dc magnetron sputtering technique from an ITO alloy target at two different oxygen pressures placing the substrates at three different lateral positions inside the chamber. The (4 4 0) oriented ITO thin films at optimal deposition conditions with high transmittance, low sheet resistance, good crystallinity and novel morphology was obtained at room temperature deposition. The structural, optical, morphological, electrical transport behavior and figure of merit imply the need in optimizing the positioning of the substrates within the chamber during deposition for achieving films of best desired properties.

Epitaxial growth of metallic buffer layer structure and c-axis oriented Pb(Mn1/3,Nb2/3)O3–Pb(Zr,Ti)O3 thin film on Si for high performance piezoelectric micromachined ultrasonic transducer

This paper reports on the development of a metallic buffer layer structure, (100) SrRuO3 (SRO)/(100) Pt/(100) Ir/(100) yttria-stabilized zirconia (YSZ) layers for the epitaxial growth of a c-axis oriented Pb(Mn1/3,Nb2/3)O3–Pb(Zr,Ti)O3 (PMnN–PZT) thin film on a (100) Si wafer for piezoelectric micro-electro mechanical systems (MEMS) application. The stacking layers were epitaxially grown on a Si substrate under the optimal deposition condition. A crack-free PMnN–PZT epitaxial thin films was obtained at a thickness up to at least 1.7 µm, which is enough for MEMS applications. The unimorph MEMS cantilevers based on the PMnN–PZT thin film were fabricated and characterized. As a result, the PMnN–PZT thin film exhibited −10 to −12 C/m2 as a piezoelectric coefficient e31,f and ∼250 as a dielectric constants εr. The resultant FOM for piezoelectric micromachined ultrasonic transducer (pMUT) is higher than those of general PZT and AlN thin films. This structure has a potential to provide high-performance pMUTs.

Influence of Aluminum concentration and substrate temperature on the physical characteristics in chemical sprayed ZnO:Al thin films

The continuous interest in the synthesis and properties study of materials has permitted the development of semiconductor oxides. Zinc oxide (ZnO) with hexagonal wurzite structure is a wide band gap n-type semiconductor and interesting material over a wide range. Chemically sprayed aluminium-doped zinc oxide thin films (ZnO:Al) were deposited on soda-lime glass substrates starting from zinc pentanedionate and aluminium pentanedionate. The influence of both the dopant concentration in the starting solution and the substrate temperature on the composition, morphology, and transport properties of the ZnO:Al thin films were studied. The structure of all the ZnO:Al thin films was polycrystalline, and variation in the preferential growth with the aluminium content in the solution was observed: from an initial (002) growth in films with low Al content, switching to a predominance of (101) planes for heavily dopant regime. The crystallite size was found to decrease with doping concentration and range from 33 to 20 nm. First-order Raman scattering from ZnO:Al, all having the wurtzite structure . The assignments of the E2 mode in ZnO:Al differ from previous investigations. The film composition and the dopant concentration were determined by Auger Electron Spectroscopy (AES); these results showed that the films are almost stoichiometric ZnO. The optimum deposition conditions leading to conductive and transparent ZnO:Al thin films were also found. In this way a resistivity of 0.03 Ω-cm with a (002) preferential growth, were obtained in optimized ZnO:Al thin films.

Optimized giant magneto-impedance effect in electroless-deposited NiFeP/Cu composite wires

In this work, NiFeP/Cu composite wires were fabricated by electroless deposition. The preparation parameters have been comprehensively investigated, including metallic salt ratio of FeSO4 to (FeSO4+NiSO4), concentration of NaH2PO2, pH value and deposition temperature. These parameters showed significant influence on the surface morphology, magnetic properties and giant magnetoimpedance (GMI) effect. As a consequence, the optimal bath composition and deposition conditions were obtained, resulting in the maximum GMI ratio (ΔZ/Z)max of 1103% at 1MHz. The optimized composite wires have showed practical potential in the application of magnetic sensors.

On-chip electrochromic micro display for a disposable bio-sensor chip

This paper reports an on-chip electrochromic micro display made of polyaniline (PANi) which can be easily made on a CMOS chip. Micro-patterned PANi thin films were selectively deposited on pre-patterned microelectrodes by using electrodeposition. The optimum conditions for deposition and electrochromism were investigated. An 8-pixel on-chip micro display was made on a Si chip. The color of each PANi film could be independently but simultaneously controlled, which means any 1-byte digital data could be displayed on the display. The PANi display had a response time as fast as about 100 ms, which means the transfer data rate was as fast as 80 bits per second.

Fabrication and study of sol-gel ZnO films for use in Si-based heterojunction photovoltaic devices

This paper considers the use of zinc oxide thin films prepared via the sol-gel route as an n-type layer in heterojunction ZnO/Si solar cells. The ZnO films were prepared via a simple spin-coating technique using zinc acetate dihydrate as a zinc precursor, isopropanol as a solvent and monoethanolamine as a stabilizing agent. Optical, structural and morphological properties of ZnO were investigated for thin films grown from sol-gel solutions with different concentrations both on glass and silicon substrates. As such, a distribution of crystallite sizes and surface topology parameters corresponding to various zinc acetate dihydrate concentrations were obtained to elucidate optimal film deposition conditions. Correlation between thin film morphology and structural characteristics of ZnO thin films was made based on atomic-force microscopy studies. Finally, our results on fabrication, characterization and simulation of ZnO/Si heterojunctions for use as photovoltaic devices are presented. Although noticeable rectifying and photovoltaic properties were observed for Al/Si/ZnO/Ti/Au devices, there appears to exist a considerable room for device improvement with simulation studies suggesting that efficiencies of the order of 24% may be obtained for devices with optimal silicon wafer passivation, i.e. with lifetimes of the order of 1000 μs.

Hard AlN films prepared by low duty cycle magnetron sputtering and by other deposition techniques

Crystalline AlN films are very attractive due to their properties such as high thermal stability and relatively high hardness and piezoelectric response. However, the deposition of dense textured AlN films with superior quality at a high deposition rate remains a challenge. In the present work, a reactive low duty cycle pulsed direct current magnetron sputtering (LDMS) process was employed to deposit AlN films on glass and silicon substrates. An arc-free discharge on the Al target was achieved by using short voltage pulses of 10 μs at a low duty cycle of 10%. The authors optimized the deposition conditions in terms of reactive gas flow, working pressure, average target power, substrate temperature, substrate bias, and the level of target erosion. With the optimized deposition conditions, the authors were able to obtain transparent crystalline AlN films with strong (002) preferential orientation and very good optical and mechanical properties: The AlN films with the highest refractive index of 2.1 present ...

Deposition and properties of Fe(Se,Te) thin films on vicinal CaF2 substrates

We report on the growth of epitaxial Fe1+δSe0.5Te0.5 thin films on 0°, 5°, 10°, 15° and 20° vicinal cut CaF2 single crystals by pulsed laser deposition. In situ electron and ex situ x-ray diffraction studies reveal a tilted growth of the Fe1+δSe0.5Te0.5 films, whereby under optimized deposition conditions the c-axis alignment coincides with the substrate [001] tilted axis up to a vicinal angle of 10°. Atomic force microscopy shows a flat island growth for all films. From resistivity measurements in longitudinal and transversal directions, the ab- and c-axis components of resistivity are derived and the mass anisotropy parameter is determined. Analysis of the critical current density indicates that no effective c-axis correlated defects are generated by vicinal growth, and pinning by normal point core defects dominates. However, for H∣∣ab the effective pinning centers change from surface defects to point core defects near the superconducting transition due to the vicinal cut. Furthermore, we show in angular-dependent critical current density data a shift of the ab-planes maxima position with the magnetic field strength.

Development and Evaluation of Flame-Assisted Dual Velocity Nanoparticle Coating System

The importance of coatings in modern science and industry is great, and the system presented in this manuscript attempts to provide a method of creating high quality nanoparticle coatings with in situ sintering of nanoparticles. Dual regime nozzle creates close to optimum conditions for particle delivery and deposition and the addition of in situ thermally assisted coating makes it more productive. Preliminary results show systems uniform coating and in situ sintering capability.

Electrochemical deposition of p-CdTe nanoparticle thin films for solar cell applications

In present work, p-type CdTe nanostructure thin films successfully synthesized on transparent conductive fluorine-doped SnO2-coated (FTO) substrate from acidic bath using three-electrode electrodeposition technique. Influence of applied potential and electrodeposition time on the structural, morphology and opto-electrical properties of the deposited films has been systematically investigated. Raman spectroscopy, low angle XRD, and HR-TEM analysis suggest that electrodeposited thin films have zinc blende cubic crystal structure. At optimized deposition conditions, we have found that CdTe thin films have direct band gap in the range 1.42–1.53 eV with a blue shift in absorption edge which may caused by quantum confinement effects in the CdTe thin films. The Hot probe experiment and Hall coefficient (RH) values confirmed the p-type semiconducting behavior of CdTe thin films. The ease of deposition of p-type CdTe nanostructure with different morphologies at room temperature provides a new insight for potential applications in hetero-junction solar cells technology.

Functional diamond like carbon (DLC) coatings on polymer for improved gas barrier performance

We have studied the optimum deposition conditions for the improvement of oxygen and carbon dioxide gas barrier performance of functional diamond-like carbon (DLC) thin films. The a-C:H: a-C:H:Si, a-C:H:N and ta-C:N thin films with 10–400nm thickness were deposited on polyethylene terephthalate (PET) substrates by the radio frequency plasma-enhanced chemical vapour deposition method. To study the microstructure of the PET coated films, we have used the Raman spectroscopy, X-ray photoelectron spectroscopy, nano-indentation and surface profilometry. The gas barrier property were analysed and found that the a-C:H:N's are 5–10 times better gas barrier properties than that of uncoated PET substrates. These thin layer PET coated thin films could be use in food packaging and biomedical applications.

(Invited) Atomic Layer Deposition of Cobalt, Nickel, and Iron Sulfides: Synthesis and Applications

Transition metal sulfides have recently aroused great attention for a variety of applications in energy conversion and storage devices. Many transition metal sulfides, such as cobalt, nickel, and iron sulfides, have shown superb electrochemical properties, so they are highly promising as candidate active materials for supercapacitors, batteries, and water-splitting electrocatalysis. Atomic layer deposition (ALD) is a well-known nanotechnology for preparing uniform, conformal coating films on complex 3D structures. Recently, ALD has gained particular attention in energy conversion and storage applications, as ALD has been demonstrated as an effective approach to uniformly and conformally load active materials onto complex 3D nanostructured electrodes. For most electrodes, their electrochemical properties are largely determined by the surface properties, and therefore conformally coating the surface by ALD is of particular importance for the device performance, as the optimization of the nanostructured geometry of the electrodes can be decoupled from the modification of the surface properties. On the other hand, however, ALD of metal sulfides is much less explored, as compared to oxides. The ALD processes for many of the important sulfides, such as CoSx, NiSx, and FeSx, are still not well established, which therefore could seriously hinder their applications in energy devices. Herein, we will present our recent progress on the ALD of CoSx, NiSx, and FeSx. The metal sulfides were all deposited using metal amidinates as the metal precursors and H2S as the sulfur source. The saturation behaviors of these ALD processes were carefully studied. Typical film properties, such as microstructure, purity, and morphology, were evaluated by various techniques including TEM, AFM, SEM, RBS, and XPS. With optimal deposition conditions, our ALD processes were able to produce high-quality, pure, smooth, and well-crystallized films of CoSx, NiSx, and FeSx. In addition, all these sulfide films were able to uniformly and conformally cover deep narrow trenches with high aspect ratio of 10:1, which demonstrated the excellent conformality of our ALD processes. We will also present a few examples to demonstrate the promising applications of these ALD sulfides in energy conversion and storage devices. ALD CoSx showed excellent electrochemical redox kinetics in alkaline aqueous solution, and therefore it was a suitable candidate active material for supercapacitors. By conformally depositing CoSx thin film on porous nickel foam electrodes, the synthesized ALD-coated electrodes showed remarkable supercapacitor performance with high specific capacitance, good rate performance, and good cycling stability. Meanwhile, ALD NiSx was found to show excellent electrocatalytic performance toward OER, and therefore it was promising for electrocatalysis and metal-air batteries. Further studies showed that the ALD NiSx converted to porous nickel oxyhydrate during electrochemical aging, and the aged product exhibited superior OER performance with good stability.